You and your tenants need to be clear about who is responsible for carrying out repairs. The tenancy agreement should clearly state which repairs you are responsible for and which are the responsibility of the tenants. If it doesn't, the default repairing obligations laid out in the Private Tenancies Order will apply.
A major gripe of tenants is that landlords take too long to carry out repairs. You must carry out repairs within a reasonable time frame. There is no legal definition of what constitutes a "reasonable" timeframe, but common sense should prevail here.
Consider the nature of the repair. Is the damaged item a necessity or a luxury? How long would you or your household be able to live comfortably without the appliance or damaged item? Are the tenants likely to have lots of extra expenses until this item is fixed? If the repair is a matter of security or is likely to seriously impact on the tenants' health, it should be considered an absolute priority.
Once a tenant has reported a repair to you, you must keep the tenants informed of your progress in dealing with the issue. Write to your tenants informing them of how you and when you intend to carry out repairs.